A wireless communication system generally uses a multi-sector approach, and performance of a Mobile Station (MS) located in a sector boundary region significantly deteriorates due to Inter-Sector Interference (ISI). Therefore, it is necessary to reduce ISI in order to improve the overall system performance of the wireless communication system.
Meanwhile, if it is possible to detect channel information of MSs, a Base Station (BS) can significantly reduce ISI by using multi-sector cooperative beam forming. Therefore, various schemes for detecting channel information of MSs have been proposed, such as a scheme of detecting channel information using a sounding signal. The scheme of detecting channel information of MSs using the sounding signal is described below.
In a wireless communication system using Time Division Duplex (TDD) Orthogonal Frequency Division Multiplexing (OFDM), because an uplink and a downlink are identical to each other in channel characteristics, when an MS transmits a sounding signal to a BS over the uplink, the BS may detect channel information of the MS using the sounding signal. For convenience of description, the wireless communication system using TDD OFDM will be referred to as a TDD OFDM wireless communication system, and one example of the TDD OFDM wireless communication system is an Institute of Electrical and Electronics Engineers (IEEE) 802.16m communication system.
However, if the MS is located in a sector boundary region, a sounding signal transmitted by the MS may interfere with a sounding signal transmitted by another MS that is in a neighbor sector, causing significant distortion.
Therefore, in the IEEE 802.16m communication system, a sounding resource reuse scheme has been proposed to reduce ISI by allowing sectors to use different sounding resources. However, because use of the sounding resource reuse scheme leads to a decrease in available sounding resources per sector, the number of MSs capable of transmitting a sounding signal without ISI while using the same sounding subchannel decreases in inverse proportion to the number of sectors. Thus, compared with an independent sounding resource distribution scheme in which all sectors use the same sounding resources, the sounding resource reuse scheme disadvantageously suffers from a decrease in Multi User Diversity (MUD) gain by opportunistic scheduling.
To overcome the shortcomings of the sounding resource reuse scheme, a multi-symbol sounding resource reuse scheme has been proposed in the IEEE 802.16m communication system. The multi-symbol sounding resource reuse scheme allows a plurality of MSs to simultaneously transmit sounding signals, by using not only Frequency Division Multiplexing (FDM) and Code Division Multiplexing (CDM) but also Time Division Multiplexing (TDM). Therefore, in the multi-symbol sounding resource reuse scheme, the same number of MSs as that in the independent sounding resource distribution scheme can transmit sounding signals without ISI.
However, the multi-symbol sounding resource reuse scheme increases in ratio of sounding resources to the total available uplink resources and thus decreases in uplink resources for data transmission, causing a reduction in data transmission efficiency.
In addition, disadvantageously, both the multi-symbol sounding resource reuse scheme and the independent sounding resource distribution scheme are inefficiently high in terms of sounding signal transmission overhead of each MS because neither scheme of allocating sounding resources considers channel information of MSs.
Therefore, there is a need for a sounding signal transmission/reception method capable of minimizing ISI while minimizing the sounding resources used.